HD 20781 e

HD 20781 e

Discovery[1]
Discovered by	Mayor et al.
Discovery date	2011, published in 2019[2]
Detection method	Radial velocity[3]
Orbital characteristics[4]
Semi-major axis	0.3374+0.0155 −0.0170 AU
Eccentricity	0.06+0.06 −0.04
Orbital period (sidereal)	85.5073+0.0983 −0.0947 d
Time of periastron	2,455,513.3912+14.3623 −16.0090 JD
Argument of periastron	70.59°+61.40° −67.58°
Semi-amplitude	2.60±0.14 m/s
Star	HD 20781
Physical characteristics
Mean radius	~2.17 R🜨 (estimate)[2]
Mass	≥14.03±1.56 M🜨[4]

HD 20781 e is a hot Neptune around the star HD 20781. The planet has a minimum mass of 14.03 Earth masses^[4] and it orbits with a semi-major axis of 0.3374 astronomical units and an orbital eccentricity of approximately 0.06.^[2][4] With the same composition as Neptune, it would have a radius of 3.79 times that of the Earth. With the same composition as Earth, it would have a radius of 2.08 times that of the Earth. It orbits near the inner edge of the habitable zone of HD 20781.^{[citation needed]}

This planet was initially reported in a 2011 preprint, which referred to it as HD 20781 c.^[1] However, the 2017 paper (published in a journal in 2019) that confirmed the planet designated it HD 20781 e, using the c designation for a different, shorter-period planet.^[4]

References

1. Mayor, M.; Marmier, M.; Lovis, C.; Udry, S.; Ségransan, D.; Pepe, F.; Benz, W.; Bertaux, J.-L.; Bouchy, F.; Dumusque, X.; Curto, G. Lo; Mordasini, C.; Queloz, D.; Santos, N. C. (2011). "The HARPS search for southern extra-solar planets XXXIV. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets". arXiv:1109.2497 [astro-ph.EP].
2. "Exoplanet Catalog HD 20781". NASA. Retrieved 4 April 2021.
3. "Planet HD 20781 e". Extrasolar Planets Encyclopaedia. Retrieved 2 January 2016.
4. Udry, S.; Dumusque, X.; Lovis, C.; Ségransan, D.; Diaz, R. F.; Benz, W.; Bouchy, F.; Coffinet, A.; Lo Curto, G.; Mayor, M.; Mordasini, C.; Motalebi, F.; Pepe, F.; Queloz, D.; Santos, N. C.; Wyttenbach, A.; Alonso, R.; Collier Cameron, A.; Deleuil, M.; Figueira, P.; Gillon, M.; Moutou, C.; Pollacco, D.; Pompei, E. (February 2019). "The HARPS search for southern extra-solar planets: XLIV. Eight HARPS multi-planet systems hosting 20 super-Earth and Neptune-mass companions". Astronomy & Astrophysics. 622: A37. arXiv:1705.05153. Bibcode:2019A&A...622A..37U. doi:10.1051/0004-6361/201731173. ISSN 0004-6361.

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